A containment builing, in its most common usage, is a steel or reinforced concrete structure enclosing a nuclear reactor. It is designed to, in any emergency, contain the escape of radiation to a maximum pressure in the range of 60 to 200 psi ( 410 to 1400 kPa). The containment is the final barrier to radioactive release (part of a nuclear reactor's Defence in depth strategy), the first being the fuel ceramic itself, the second being the metal fuel cladding tubes, the third being the reactor vessel and coolant system.